Laser reactive dyes for DVD copy protection system

ABSTRACT

A method and system for providing copy-protected optical medium using transient optical state change security materials capable of changing optical state when exposed to a wavelength of about 630 nm to about 660 nm and software code to detect such change in optical state.

RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/418,898 filed Apr. 17, 2003, which claimspriority to U.S. Provisional Patent Application Nos. 60/389,223 filedJun. 17, 2002, 60/390,647 filed Jun. 21, 2002, 60/391,773 filed Jun. 25,2002, 60/391,857 filed Jun. 26, 2002, and 60/393,397 filed Jul. 2, 2002,the disclosure of each which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to transient optical statechange security materials reactive to a wavelength of about 630 nm toabout 660 nm, in particular to wavelengths produced by DVD opticalreaders. Such materials may be used by directed application to opticalmedium to effectuate copy-protection. More specifically, the materialsmay be used to manufacture optically readable digital storage mediumthat protects the information stored thereon from being copied usingconventional optical medium readers, but permits reading of theinformation from the digital storage media by the same readers.

2. Description of the Related Art

Data is stored on optical media in the form of optical deformations ormarks placed at discrete locations in one or more layers of the medium.Such deformations or marks effectuate changes in light reflectivity. Toread the data on an optical medium, an optical medium player or readeris used. An optical medium player or reader conventionally shines asmall spot of laser light, the “readout” spot, through the discsubstrate onto the data layer containing such optical deformations ormarks as the medium or laser head rotates. Two common types of opticalmedia are the CD disc, providing a maximum storage space of about 650megabytes of data on a single-side (SS), single-layer (SL) disc, and theDVD disc providing about 4.37 GB (1GB=2³¹ bytes) on a single-sided (SS),single-layer (SL) disc. The ECMA Technical Committee TC31 wasestablished in 1984 for the standardization of Optical Discs and OpticalDisc Cartridges, making contributions to ISO/IEC SC23 with respect toInternational Standards.

The vast majority of commercially-available software, video, audio, andentertainment pieces available today are recorded in read-only opticalformat. One reason for this is that data replication onto read-onlyoptical formats is significantly cheaper than data replication ontowritable and rewritable optical formats. Another reason is thatread-only formats are less problematic from a reading reliabilitystandpoint. For example, some CD readers/players have trouble readingCD-R media, which has a lower reflectivity, and thus requires ahigher-powered reading laser, or one that is better “tuned” to aspecific wavelength.

In conventional “read-only” type optical media (e.g., “CD-ROM”), data isgenerally encoded by a series of pits and lands that are metallized. Areadout spot directed from the non-metallized side is reflected in amanner that the light of readout spot is reflected back into aphotosensor in the reader. When referenced from the laser reading side,pits are technically referred to as bumps. The transitions between pitsand lands, and the timing in between such transitions, represent channelbits. Thus the pit and lands in themselves are not representations of asequence of zeros or ones. Typically, in CDs 14 channel bits make up adata symbol that translates to an 8 bit data value, in a processreferred to as 8 to 14 modulation (EFM). DVD uses a modified version ofEFM, known as EFM+ to convert 8-bit data directly into 16 channel bits.The NRZI (non-return to zero inverted) waveform representation is usedto interpret the binary sequence on the disc.

Microscopic pits formed in the surface of the plastic medium arearranged in tracks, conventionally spaced radially from the center hubin a spiral track originating at the medium center hub and ending towardthe medium's outer rim. The pitted side of the medium is conventionallycoated with a reflectance layer such as a thin layer of aluminum orgold. The “pits” as seen from the metallized side, are also referred to“bumps” when referencing view from the laser-read side. A lacquer layeris typically coated on the pit side as a protective layer.

The intensity of the light reflected from a read-only medium's surfacemeasured by an optical medium player or reader varies according to thepresence or absence of pits along the information track. Asdefect-induced errors may interfere with read, all optical discs employerror management strategies to eliminate the effect of such errors.

The optical reader, such as the CD or DVD reader, has the job of findingand reading the data stored as bumps on the disc. In a conventionalplayer a drive motor spins the disc. A laser and lens system focus lighton the bumps, and an optical pickup head (PUH) receives reflected light.A tracking mechanism moves the laser assembly so that the laser's beamcan follow the spiral track, conventionally moving the laser outwardfrom the center as the disc is played. As the laser moves outward fromthe center of the disc, the bumps move past the laser faster, as thespeed of the bumps is equal to the radius times the speed at which thedisc is revolving (rpm). A spindle motor is conventionally employed toslow the speed of the disc when the laser is reading further and furtherout from the center of the disc permitting the laser to read at aconstant speed, such that the data is read from the disc at a constantspeed.

The semiconductor laser utilized, the spread of its wavelength, and itsoperational temperature affect the wavelength read by the pick up head(PUH) of the reader. DVD readers presently utilize lasers that produce awavelength of about 630 to about 660 nm, with standard DVD readersmeasuring a wavelength of 650±5 nm and standard DVD-R readers measuringa wavelength of 650 +10/−5 nm. As would be understood by one of skill inthe art, the PUHs can detect only those reflected beams that fall withina certain angular deviation from the incident beam. For example, atypical DVD-R requires that the radial deviation be no more than ±0.80°and tangential deviation no more than ±0.30°.

Optical media of all types have greatly reduced the manufacturing costsinvolved in selling content such as software, video and audio works, andgames, due to their small size and the relatively inexpensive amount ofresources involved in their production. They have also unfortunatelyimproved the economics of the pirate, and in some media, such as videoand audio, have permitted significantly better pirated-copies to be soldto the general public than permitted with other data storage media.Media distributors report the loss of billions of dollars of potentialsales due to high quality copies.

Typically, a pirate makes an optical master by extracting logic datafrom the optical medium, copying it onto a magnetic tape, and settingthe tape on a mastering apparatus. Pirates also sometimes use CD or DVDrecordable medium duplicator equipment to make copies of a distributedmedium, which duplicated copies can be sold directly or used aspre-masters for creating a new glass master for replication. Hundreds ofthousands of pirated optical media can be pressed from a single masterwith no degradation in the quality of the information stored on theoptical media. As consumer demand for optical media remains high, andbecause such medium is easily reproduced at a low cost, counterfeitinghas become prevalent.

WO 02/03386 A2, which asserts common inventors to the presentapplication, discloses methods for preventing copying of data from anoptical storage media by detecting optical dis-uniformities or changeson the disc, and/or changes in readout signal upon re-reading of aparticular area on the optical storage medium, in particular thosecaused by light-sensitive materials, such as dyes, which may affect thereadout wavelength by absorbing, reflecting, refracting or otherwiseaffecting the incident beam. Software control may be used to deny accessto content if the dis-uniformity or change in read signal is notdetected at the position on the disc wherein the dis-uniformity orchange is anticipated. The disclosure of WO 02/03386 A2 is incorporatedherein in its entirety by reference.

A preferred embodiment described in publication WO 02/03386 A2 compriseslight-sensitive materials are optically-changeable security materialsthat are positioned upon the optical disc in a manner that they do notadversely affect the data-read of the readout signal in one opticalstate but upon exposure to the wavelength of the optical reader incidentbeam covert to a second optical state, preferably in a time-delayedfashion, that does affect the data-read of the readout signal. In apreferred embodiment described in WO 02/03386 A2, theoptically-changeable security material only transiently changes opticalstate and its optical state reverts over time.

It has been discovered by the present inventors that the optimalcharacteristics for such preferred transient optically-changeablesecurity materials described in publication WO 02/03386 A2 depend upon anumber of factors, including, the characteristics of the incident beamgenerated by the laser reader used (such as the beam intensity andwavelength), the particular materials used to fabricate the optical discin particular with respect to the optical characteristics of suchmaterials with respect to the reading beam (such as refractive index andbirefringence), the particular formatting of the disc (such as pitdepth), where the optically-changeable security material is positionedon or within the disc (e.g., on the surface versus in a layer of thedisc/in the data section of the disc versus), the opticalcharacteristics of other materials that may be introduced to effectuateincorporation of the optically-changeable security material onto or intothe disc, the characteristics of the pickup head (PUH) of the opticalreader in particular with respect to readout wavelength and angle ofdeviation permitted for pickup of reflected light emanating from theincident beam, the reading characteristics of the optical reader systemin particular related to scan velocity, the time for re-scan, androtational speed of the disc. For example, the material should notchange state too quickly so as not to allow the PUH to observe bothstates. On the other hand, it should not change state too slowly so asto eventuate in a disc that would take non-commercially acceptable timesfor validation of the disc and read.

An optimal transient optical state change security material should bethermally and photochemically stable under conditions of optical use andat ambient conditions for a significant period of time. It should besoluble in a matrix that comprises the disc, or that can beadheredly-applied to the disc. An optimal transient optical state changesecurity material should revert to its state without the need forextraneous inputs of energy, and should demonstrate a change in opticalstate at the incident wavelength of the reader.

There is a need for optical state change security materials that may beemployed in a manner described in WO 02/03386 A2 to effectuatecopy-protection of optical discs, in particular DVDs, that conform toISO/IEC standards when read by their respective ISO/IEC standardizedreaders. In particular there is a need for identifying materials thatmay be used in such copy protection methodologies without requiringmodification to optical medium readers.

DEFINITIONS

“Data Deformation”: a structural perturbation on or in an item thatrepresents stored data and can be read by an optical reader.

“Dye”: an organic material detectable by optical means.

“Fabry-Perot Interferometer”: an Interferometer making use of multiplereflections between two closely spaced reflective surfaces, andtypically has a resolvance of λ/Δλ=m r/1−r

“Interferometer”: a device employing two or more reflective surfaces tosplit a beam of light coming from a single source into two or more lightbeams which are later combined so as to interfere in a constructive ordestructive manner with each other.

“Optical Medium”: a medium of any geometric shape (not necessarilycircular) that is capable of storing digital data that may be read by anoptical reader.

“Optical Reader”: a Reader (as defined below) for the reading of OpticalMedium.

“Optical State Change Security Material”: refers to an inorganic ororganic material used to authenticate, identify or protect an OpticalMedium by changing optical state from a first optical state to a secondoptical state.

“Permanent Optical State Change Security Material”: refers to aTransient Optical State Change Security Material that undergoes changein optical state for more than thirty times upon read of the OpticalMedium by an Optical Reader.

“Reader”: any device capable of detecting data that has been recorded onan optical medium. By the term “reader” it is meant to include, withoutlimitation, a player. Examples are CD and DVD readers.

“Read-only Optical Medium”: an Optical Medium that has digital datarepresented in a series of pits and lands.

“Recording Layer”: a section of an optical medium where the data isrecorded for reading, playing or uploading to a computer. Such data mayinclude software programs, software data, audio files and video files.

“Re-read”: reading a portion of the data recorded on a medium after ithas been initially read.

“Transient Optical State Change Security Material”: refers to aninorganic or organic material used to authenticate, identify or protectan Optical Medium by transiently changing optical state between a firstoptical sate and a second optical state and that may undergo such changein optical state more than one time upon read of the Optical Medium byan Optical Reader in a manner detectable by such Optical Reader.

“Temporary Optical State Change Security Material”: refers to an OpticalState Change Security Material that undergoes change in optical statefor less than thirty times upon read of the Optical Medium by an OpticalReader.

For the purpose of the rest of the disclosure it is understood that theterms as defined above are intended whether such terms are in allinitial cap, or not.

SUMMARY OF THE INVENTION

The present invention provides a for dyes and dye systems which exhibita reversible change in optical state which is detectable by a readerupon exposure of such dyes and dye systems to a wavelength of about 630to about 660 nm. In a preferred embodiment, such dyes and dye systemsact as transient optical state change security materials, providing fora change in optical state that can be repeated numerous times uponexposure to/and removal from such wavelength. That is, the presentinvention provides a method for ascertaining those compounds displayingtransient characteristics induced by exposure to read beam of an opticalreader such that the change can be detected by the uptake head of theoptical reader.

In one preferred dye system embodiment, the dye system on an opticaldisc comprises: (1) a dye that rapidly changes optical state from afirst unactivated optical state to a second activated optical state inresponse to a wavelength of about 630 to about 660 nm which isdetectable by the uptake head of an optical reader when the dye is inits second optical state, but not the dye is in its first optical state;(2) a dye-carrying polymer in which the dye is dispersed; and (3) amaterial that aids in reducing the reversal time of the dye from itssecond activated optical state back to its first unactivated opticalstate. Optionally such system may also comprise a material that aids inreducing the time to the second activated optical state from the firstunactivated optical state. The optical state change in any opticallymeasurable manner, for example in causing a change in reflection and/orrefraction, as long as the optical change can be detected. For example,in one embodiment the dye/dye system changes the percent reflectance onthe optical disc by approximately 25% to approximately 30% which hasbeen seen to be sufficient for detection at the pickup head.

One particularly useful class dyes capable of being activated by awavelength of about 630 to about 660 nm that have been identified are:

where R₆, R₇, R₈, and R₉ are alkylamino and R₁, R₂, R₃, R₄ and R₅ areselected from the group consisting of hydrogen, alkyl, aryl, alkoxy,thioalkoxy, alkylamino, nitro, amino and halogen. In one preferredembodiment R₆, R₇, R₈, and R₉ are each, or independently, propyl orhexyl and R₁, R₂, R₃, R₄ and R₅ are hydrogen or alkyl.

Such dye substances can be incorporated into a dye system whichcomprises an electron donor agent (ED)/electron transfer agent (ETA).Such compounds are electron rich and provide electrons to the dyemolecule for example once the dye molecule is reduced to thecorresponding leuco form. In the presence of laser light, thisphenomenon may be referred to as photoreduction.

Non-limiting examples of ETAs which may be incorporated into the dyesystem include triethanol amine, diethanol amine, TMG, DMEA, DEMEA,TMED, EDTA, Bis-Tris, p-tolylimido diethanol, N-tert-butyldiethanolamine, 4-morpholine ethanol, 1,4-bis-2-hydroxyethyl piperazine, bicineand BES.

The ETA may be incorporated into the polymeric base of a dye systemphysically or chemically. For example, a useful ETA may be bound to therepeating polymeric unit. For example, a compound of the followingstructure has been found to be a useful ETA: as well as other compoundscomprising a polymer having a bis(2-hydroxy ethyl) amino functionality.A preferred polymer may be in the molecular weight range of 50-100k.

Other non-oxygen associated ETAs may be used, such as a combination ofreductants such as Fe (II)-Fe (III).

The dye and/or dye system may be used on an optical disc to effectuatedata changes on the disc, preferably at the bit level code. As describedin the applications referenced above, a security software can be sued toconfirm the change in code. The dye/dye system is preferably placed in amanner on the disc so as not to alter playability on industry compliantDVD devices.

As would be understood by one of ordinary skill in the art, the dyes/dyesystems employed on an optical disc should be selected such that they donot decay or degrade and such they are safe.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof the specification, illustrate presently preferred embodiments of theinvention, and together with the general description given above and thedetailed description of the preferred embodiments given below, serve toexplain the principles of the invention.

FIG. 1 illustrates a multi-layer optical disc embodiment of the presentinvention having reflective layer, dye layer, and transparent substrate;

FIG. 2 is a chart of reflectivity versus time in regard to a dye systemunexposed to DVD reader laser light, exposed to DVD reader laser light,and recovered from exposure to DVD reader laser light;

FIG. 3 is a real time plot of pit/land signal with respect to the dyesystem of FIG. 2;

FIG. 4 is an atomic force microscope photo of a multi-depth pit masterwhich may be used to form a multi-depth pit disc; and

FIG. 5 is an atomic force microscope photo of a multi-depth pit discwith dye/dye system of the present invention being coated on the highestbumps (deepest pits).

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for transient transient optical statechange security materials reactive to a wavelength of about 630 nm toabout 660 nm, in particular to wavelengths produced by DVD opticalreaders. The transient optical state change security materials may beused to manufacture optically readable digital storage medium thatprotects the information stored thereon from being copied usingconventional optical medium readers, but permits reading of theinformation from the digital storage media by the same readers.

As disclosed in WO 02/03386 A2, which asserts common inventors to thepresent application, transient optical state change security materialsmay be used to effectuate copy-protection of an optical disc byproviding a change in optical state upon activation of the material bythe incident reading laser beam, that is of such character that upon asecond read of the area of the disc where the transient optical statechange security material is located a change in data read is detected atthe optical pickup head. The materials may be used to cause anuncorrectable error upon re-read of such a character that the errorinterferes with copying function of most optical readers that requireoversampling in the copying process, and/or a uncorrectable/correctableerror, or a change in interpretation of a data read, that due to analgorithm on the disc, which may be incorporated as an encryption code,and/or an algorithm incorporated into the reader and/or componentassociated with the reader, is used to authenticate the disc and permitcopying only upon authentication.

The materials may also be used to effectuate complementary datasequences (CDSs) both of which are interpreted as valid, both of whichare interpreted as erroneous, or one of which is interpreted as validand the other as erroneous, or one of which is interpreted as erroneousand the other as valid. That is, the for example, the materials may beused to cause a pit to disappear altogether of change its length becausepart of it disappeared. It is preferred that the material be conformalwith the data structure. Copy protection may be effected using CDSs by,for example, having the first valid data read attributable to thematerial in its unactivated state directing the reader to an erroneoustrack on the disc, while having the second valid data read attributableto the material in its activated state directing the reader to thecorrect track for further effectuating of the read. As would beunderstood, copying of the disc in such situation is hampered byresampling by the copying device (which reads two different valid datareads). When such error is detected, re-seek algorithms internal to thedrive will cause the data stored in the tracking control to be re-read.If the transient optical state change security material, which may betemporary or permanent, is in its second state, and the second state isselected as to allow the underlying data to be read, the new addresswill be correct and the content on the disc will be able to be read. Inone embodiment of such “spoofing” technique for copy-protection, thematerial is placed at the subcode level in the lead-in zone thuseffecting the table of contents. The material may be placed at themicrolevel in the CRC field. A copy of the disc incorporating datahaving the first valid data read alone would not work due to the failureof the data to direct subsequent reading to the correct track. Thetransient optical state change security material may also provide for avalid data state read in a first optical state, but an uncorrectableread error in a second optical state, making it significantly moredifficult for a would-be copier of the disc to reproduce an operabledisc by incorporating an uncorrectable error, such as a physicaldeformation, into the disc.

By “correctable error” it is meant an error which is correctable by theECC used with respect to the optical disc system, while an“uncorrectable error” is an error which is not correctable. ECC arealgorithms that attempt to correct errors due to manufacturing defectssuch that the opticaldisc works as intended. Error detection methods areconventionally based on the concept of parity. All optical discs employerror management strategies to eliminate the effect of defect-inducederrors. It has been found that even with the most careful handling, itis difficult to consistently manufacture optical discs in which thedefect-induced error rate is less than 10⁻⁶. Optical recording systemsare typically designed to handle a bit-error rate in the range of 10⁻⁵to 10⁻⁴. The size of the defect influences the degree of errorassociated with the defect. Thus some defects create such a marginalsignal disturbance that the data are almost always decoded correctly.Slightly smaller defects might induce errors hardly ever. Macro or microdepositions may also be used to cause correctable or uncorrectableerrors. For example, micro depositions may be of such size as to kill adata group that is fixable by C₁/C₂ of ECC of a CD, but if applied tokill enough groups may cause an uncorrectable error detectable by suchsoftware.

The type of transient perturbation that is desired to be effectuated,whether a correctable error, uncorrectable error, two or morecomplementary valid data sequences, a valid data sequence and acorresponding invalid data sequence and/or other detectable change atthe optical pickup head, will dictate where on the disc the transientoptical state change security material will be placed. For example, if adata change detectable by the optical pickup head is desired, thematerial should not of course be placed in the clamping zone. If thereis a valid to valid, or erroneous to erroneous data state change, inorder to allow easy detection it is preferred that the data state changecauses a change in the values read. In error state to error statechanges the level of severity of the errors preferably is different,thereby aiding detectability.

The present invention discloses transient optical state change securitymaterials (both temporary optical state change security materials, andpermanent optical state change security materials) that change opticalstate upon exposure to a wavelength produced by DVD readers. Thematerial, which may comprise a dye or dye system, transiently changesthe signal read by the pickup head by changing, for example thereflectivity of the laser beam when the material is in its activatedstate versus its unactivated state. Typically, when used for theproduction of copy protected optical discs, the dye acts to change adetectable parameter, e.g. reflectivity, at a few selected pit/landstructures. A typical dye system comprises a dye which changes from afirst unactivated optical state to a second activated optical state uponexposure to a wavelength produced by a DVD reader, e.g. form about 630nm to about 660 nm, a electron donor agent or electron transfer agentwhich aids in the conversion of the activated second optical state backto the unactivated first optical state, and a polymer. It has been foundthat the system composition affects the laser activation, the rate andintensity of optical sate change in response to an activationwavelength, and the conformal application of the dye/electron donor tothe disc.

A DVD read laser has a spectra centered about 650 nm wavelength. Theabsorption spectra for methylene blue in solution shows an absorptionmaxima at 655 nm. While such dye might appear to be useful in itself asa transient optical state change material, when applied to optical discit was observed that the absorption underwent a bathochromic shift withthe spectrum having an absorption maxima at about 590 nm due toaggregration. The absorption spectrum was of the compound was found tobe modifiable by altering the steric bulk on the nitrogen. A preferredstructure in regard to a a methylene blue backbone comprised improvedelectron withdrawal at the positively charged side chain nitrogen, andelectron withdrawal at the other side chain nitrogen.

One particularly useful class dyes capable of being activated by awavelength of about 630 to about 660 nm that have been identified are:

where R₆, R₇, R₈, and R₉ are alkylamino and R₁, R₂, R₃, R₄ and R₅ areselected from the group consisting of hydrogen, alkyl, aryl, alkoxy,thioalkoxy, alkylamino, nitro, amino and halogen. In one preferredembodiment R₆, R₇, R₈, and R₉ are each, or independently, propyl orhexyl and R₁, R₂, R₃, R₄ and R₅ are hydrogen or alkyl.

Preparation of Exemplar Thiazine Compounds Useful for Copy-ProtectedDVDs EXAMPLE 1 Propyl and Hexyl Analogs of Methylene Blue

To shift the absorption maxima closer to 650 nm, propyl (MB-3) and hexyl(MB-6) analogs of methylene blue were synthesized using the proceduredescribed by Mellish et al. as set forth below.

The absorption maxima of the compounds when coated onto optical mediawas in the expected range and the change in optical state was detectableby the PUH. The optical density of 5% poly-HEMA (poly-2-hydroxyethylmethacrylate), 250 mg MB-3, and 160 mg Bis-Tris(2,2-Bis(hydroxymethyl)-2-2′,2″-nitroethanol) on one disc was 0.22absorbance units at 650 nm and the optical density on another disc using325 mg MB-3, 5% poly-HEMA and 160 mg Bis-Tris was 0.3 absorbance units.The disc with optical density of 0.22 absorbance units demonstratedabout a 18% photobleach at 650 nm. The disc with optical density 0.32absorbance units demonstrated about a 30% photobleach at 650 nm.

An ETA or ED (electron donor agent) is a compound that is electron richand provides electrons to the dye molecule that is being reduced to thecorresponding leuco form. In the presence of laser light, thisphenomenon is called photoreduction:

ETAs are particularly useful in a dye system of the present inventionwhen photoreduction is a principle means of optical state change back tothe unactivated state. ETA's that can be used in this system include,but not limited to, triethanol amine, diethanol amine, TMG, DMEA, DEMEA,TMED, EDTA, Bis-Tris, p-tolylimido diethanol, N-tert-butyldiethanolamine, 4-morpholine ethanol, 1,4-bis2-hydroxyethyl piperazine, bicineand BES. Such ETAs have been found to photobleach the system using a DVDlaser on the pulsetec. In general percdent photobleach observed wasdirectly proportional to the amount of ETA added in the system, but itwas found that there is a limit to the amount of ETA that can betolerated in the system after which discs are not playable.

Preparation of Exemplar Copy-Protected DVD EXAMPLE 2 Optical Disc HavingDye System Comprising MB-3

250 mg of MB-3 dye was added to a 25 ml 4% polymer solution in 1-methoxy2-propanol Aldrich catalog No. 484407 and 150 mg of Bis-Tris was added.The resulting solution was stirred vigorously on a shaker for 30-60 min.The final solution was filtered through a 0.2 μm filter and was used tospin coat optical discs. The spin coater used for this purpose was modelP-6708D manufactured by Specialty Coating Systems.

EXAMPLE 3 Optical Disc Having Dye System Comprising MB-3

To a 25 ml solution of 4% PolyHEMA in methoxy propanol was added 300 mgof MB-3 and 150 mg of Bis-Tris. The solution was stirred on a shaker for30 min and filtered through 0.2 um filter and the filtered solution wasused to coat discs using a spin coater Disc No. 1854-1857.

A two component dye system is yet another embodiment of the invention.In such system, the ETA is combined chemically with the polymer. It hasbeen found by the present inventors that polymers that have ETA appendedwill photobleach. Useful electron transfer polymers include, but are notlimited to: a) any polymer containing the bis(2-hydoxyethyl)aminofunctionality as shown below, b) homo-polymers or copolymers with vinylacetate or methacrylate containing the (2-hydoxyethyl)aminofunctionality.

and c) any other polymer in Mol wt. range 50-100K that is soluble inmethoxy propanol and having a bis(2-hydroxy ethyl) amino functionality.

EXAMPLE 4 ETA Polymer-Methylene Blue Dye System

Polyethylenimine which was 80% ethoxylated in water was adjusted to a pHof about 8 using concentrated HCl and methylene blue added to bring theabsorbance to 3. Photobleach of the system was seen with a simpleoverhead projector to be in the range of 2-3 seconds with oxidation backto unactivated state in approximately 2-3 minutes.

Combinations of reductants such as Fe (II)-Fe (III) can be used for anoxygen free system. For example, the catalytic effect of ferrous ion onthe photochemical bleaching of thionine in the presence ofdiethylallylthiourea is related to the present work on methylene blue.On irradiating a 0.001% aq. solution of thionine containing 0.0075 mol.per liter, the dye bleaches in 1-2 sec. The color returns again in 1-2sec. after removal of the light. Similarly the leuco form of the dyewill return to the original colored form in the presence of weak-strongoxidizing agents such as bromine or silver halides to name a few.

Now turning to the figures, FIG. 1 illustrates a cross-section of anoptical medium embodiment comprising a transient optical state changesecurity material between two substrates. FIG. 4 is an atomic forcemicroscope photo of a multi-depth pit master which may be used to form amulti-depth pit disc. Such multi-depth pit (i.e. heightened bump) may beuseful for easing application of the dye to select pits (bumps from theread side). FIG. 5 is an atomic force microscope photo of an exemplarmulti-depth pit disc with dye system of the present invention beingcoated on the highest bumps (deepest pits). FIG. 2 is a chart ofreflectivity versus time in regard to a dye system before and duringexposure to a DVD reader laser light, and after it has returned to theunactivated state. FIG. 3 is a real time plot of pit/land signal withrespect to the dye system of FIG. 2.

Optimization of transient optical state change security materials for aparticular reader is influenced in part by the particular materials usedto fabricate each layer of the optical disc itself, and the material'sposition vis-à-vis such layers and the incident laser beam. It istherefore useful when selecting for such optimal security materials withrespect to a particular reader that the material be placed on a disc ofsimilar fabrication and placed for testing purposes in a manner similarto how they are ultimately to be placed.

Placement of Transient Optical State Change Security Materials WithRespect to Optical Data Structures on the Optical Discs

In General

As disclosed in WO 02/03386 A2, the transient optical state changesecurity materials may be placed anywhere on or within the opticalmedium so long the PUH can detect the change in optical state. Suchsecurity materials may advantageously be placed in or on the opticalmedium on either the laser incident surface (“LI Method”) or thepit/land surface (a.k.a. the focal plane) of the optical medium (“FPMethod”). Advantageously, changes in reflectivity, absorbance, opticalclarity, and birefringence due to the application of the securitymaterials may be monitored to assure that such materials do notinterfere with industry standards, suggestive that the optical mediummight not adequately perform in its reader. Audio Development's CD-CATSand DVD-CATS testers may be used to measure servo responses, HF signalamplitudes, and error behaviors.

Surface Application

The transient optical state change security materials may be appliedtopically to a surface of the optical medium or component of the opticalmedium during manufacture. Topical surface application may be by any ofthe imprinting techniques known to those of ordinary skill in the art,including, but not limited, air brush, industrial ink jet printing,desktop ink jet printing, silkscreen printing, sponge/brush application,air brushing, gravure printing, offset lithography, oleophilic inkdeposition onto a wetted surface.

The material may also be spin coated. Spin coating a layer comprisingthe transient optical state change security materials may be a preferredmethod of application due to precision and uniformity requirements. Onlyminor process modification are typically necessary to implement in-linedeposition by spin coating. The spin coat may be applied using any meansknown to those of ordinary skill in the art. For example, a precise,small quantity of dye may be placed in a radial line with the discstationary and the disc subsequently spun to produce a precisely coatedarea. Conventionally spin coating entails a first ramp of accelerationto first speed, a first dwell time at first speed, a second ramp ofacceleration to second speed, a second dwell time at second speed, athird ramp of acceleration to third speed, a third dwell time at thethird speed, deceleration, and post conditioning (baking/drying/curingat defined temperatures for defined periods of time) The spin profilemay be advantageously controlled to produce the desired coating. It ispreferred that when such security materials are placed on an otherwiseexposed surface of the completed optical medium, that the securitymaterials be coated to protect against wear of the security material dueto handling of the optical medium. Thus, for example when securitymaterial is applied to the laser-incident surface of a completed opticaldisc, it is advantageous that a hard-coating be placed over the securitymaterial to prevent wear or removal of the security dye from suchsurface.

The transient optical state change security materials may be coated ontothe pit-surface prior to lacquering of the optical medium, addition of asecond substrate (DVD) and/or application of any label. The lateraddition of such materials helps protect against removal and degradationof the security material. Any covering over the security material mayfurther comprise a special filtering material, such as GE filteringpolycarbonate.

The transient optical state change security materials may be placed atthe pit/land surface.

In one embodiment, pit/land placement may makes use of pit geometriesneeded to accommodate dye deposition at the focal plane of the disc.Techniques such as Atomic Force Microscopy (AFM) may be used to verifydimensions. Optimal pit geometries for the particular security materialmay be determined by spin coating the material onto a surface havingvariable pit depths, determining which pits contain the materials as by,for example, microscopy, and determining which pit dimensions which mayhold material after spin coating, actually allow for playback withoutthe dye in them, and without errors. The optical medium with thematerial and determined pit geometries is then checked to determinewhether a dual data state, error to valid, or valid to error, may beproduced. Different radii, depths etc. may be investigated.

For example, without any limitation, a variable pit depth glass masterfor a CD may be made using a 350 nm thick photoresist and LBR (laserbean recorder) power step series, as to form 13 steps in random order,except for nominal depth tracts which contain 50 MB of pseudo-randomuser data, as follows: 160nm (nominal pit depth), 120 mn, 150 nm, 180nm, 160 nm (nominal), 210 nm, 240 nm, 270 nm, 160 nm (nominal), 300 nm,320 nm, 350 nm, 160 nm (nominal). Similarly, a variable pit depth masterfor DVD may be made using a 200 nm thick photoresist and LBR power stepseries, as to form 13 steps in random order except the nominal depthtracks, wherein each track contains 360 MB of pseudo-random user data,as follows: 105 nm (nominal), 80 nm, 95 nm, 110 mn, 105 nm (nominal),125 nm, 140 nm, 155 nm, 105 nm, 170 nm, 185 nm, 200 nm, 105 nm(nominal). The discs can be spun coat with material comprising transientoptical state change security material, the pit depths incorporating thematerial determined, and pits of such dimensions analyzed for whetherthe impact upon read without the material when the optical medium iscompleted (metallized, lacquered etc.)

Detection from the laser-read side may be enhanced by including one ormore deep pits in the substrate, such pits being made using a masterdesigned to form multiple-depth pits. Detection may also be improved byoptimizing pit geometry of the deep pits. Variable pit depth glassmasters may be fabricated. For example, 350 nm thick photoresists andLBR power step series may be employed to produce different stepsincluding nominal depth tracks for pseudo-random user data

The pits may advantageously be placed only in the outer 5 mm of thedisc, or in the lead out region of the disc. In such case, only theouter portion of the disc, or lead out region, need be coated.

The deep pits may also be used to form an interferometer by placement ofthe security material with respect to the deep pit prior tometallization.

Placement of Transient Optical State Change Security Material inPolycarbonate with Formation of Extended Pits Upon Molding Prior toMetallization to Form an Interferometer Along the Extended Pits

The transient optical state change security material may incorporatedinto the polycarbonate and deep pits (bumps from the read side) flankingone or more lands molded into the polycarbonate at predeterminedlocations. The pits may be constructed to be of such depth that as toform an interferometer between the enlarged bumps, when viewed from theread side, that fail to reflect sufficiently for read by the PUH of theoptical reader when the security material changes state due exposure tothe incident read laser beam. This system therefore employs twocomponents: the transient optical state change security materialdistributed throughout the polycarbonate, and a interferometer, of theFabry-Perot type (“FPI”).

The FPI works by varying the amount of light reflected back to a source.This variation is dependent on the intensity, angle and wavelength ofthe light entering the interferometer. The physical construction of anFPI, when viewed from the read-side, can be effectuated during thestamping procedure by creating one or more pits of extended depthflanking one or more lands. The glass master advantageously is modifiedto create such pits of extended depth. The deep pits act as the walls ofthe FPI, while the reflective land at the bottom acts as the primaryreflective surface. By carefully selecting the transient optical phasechange security material, under one set of conditions (intensity,wavelength, angle) there will be considerable reflectivity back to thesource, while under a second set of conditions, there will besignificantly less light reflected back to the source. These two stateswill be driven by the security material placed in the polycarbonate(PC).

If the interferometer is appropriately manufactured, and the transientoptical state change security material chosen, the material in the PCwill be essentially transparent to the PUH and all data will be read atone state. During the read, the material will absorb energy. When enoughenergy has been absorbed by the material its transmittance will decrease(less energy passes through) and it will cause a slight change inrefractive index. In the second state with the transmittance decreased,if property designed, the input energy threshold for the FPI can be madeto be crossed, and very little signal will be reflected. By carefullyselecting the security material and its concentration in the PC, one cancause enough signal to the optical data structures so as to be able toread such data. One the other hand, if RI is changed when the materialis activated by the read beam, the security material and itsconcentration, and the depths of the pits (from the non-read side)should be such as to result in a change in wavelength that crosses theFPI threshold resulting in a reduction in reflectivity, but thewavelength change should be small enough that normal sized optical datastructures may still be resolved. It should be noted that the disc mayhave to be preformatted, such as is the case with CD-RW, if theautomatic gain control (AGC) is inappropriately invoked based on ATIPinformation.

Placement of Transient Optical State Change Security Material BetweenSubstrates Comprising the Optical Medium

Dye may be deposited and encapsulated between substrates, for example anambient protective polycarbonate, such as that produced by GeneralElectric. Such placement eliminates optical hard coating, uses existingmanufacturing processes, provides protection, and expands the possibledye chemistries that might be employed because read laser optical powerdensity is, for example, greater at 0.6 mm from the pit surface than at1.2 mm.

STATEMENT REGARDING PREFERRED EMBODIMENTS

While the invention has been described with respect to preferredembodiments, those skilled in the art will readily appreciate thatvarious changes and/or modifications can be made to the inventionwithout departing from the spirit or scope of the invention as definedby the appended claims. All documents cited herein are incorporated intheir entirety herein.

1. A method for fabricating an optical medium readable by an opticalreader, said method comprising the steps of: (a) molding a substrate soas to have a first major surface with information pits and informationlands thereon and a second major surface that is relatively planar; (b)applying a transient optical state change security material capable ofconverting from a first optical state to a second optical state uponexposure to the laser of said optical reader to at least a position ofsaid first major surface; (c) applying a reflective material over thefirst major surface so as to cover said information pits and informationlands; wherein the transient optical state change security materialcomprises:

where R₆, R₇, R₈, and R₉ are alkylamino and R₁, R₂, R₃, R₄ and R₅ areselected from the group consisting of hydrogen, alkyl, aryl, alkoxy,thioalkoxy, alkylamino, nitro, amino and halogen.
 2. The method of claim1 wherein R₆, R₇, R₈, and R₉ are propyl or hexyl and R₁, R₂, R₃, R₄ andR₅ are hydrogen.
 3. An optical disc readable by an optical readergenerating a reading beam comprising: a substrate having first majorsurface with one or more information pits and lands thereon, and asecond major surface that is relatively planar, said information pitsand lands convertible into digital data bits when read through thesecond major surface by said reading reading beam of said opticalreader; a transient optical state change security material capable ofexisting in a first unactivated state and a second activated state onsaid first or second major surface, said transient optical statesecurity material comprising:

where R₆, R₇, R₈, and R₉ are alkylamino and R₁, R₂, R₃, R₄ and R₅ areselected from the group consisting of hydrogen, alkyl, aryl, alkoxy,thioalkoxy, alkylamino, nitro, amino and halogen; and a reflective layerpositioned over said information pits and lands; wherein in at least twoor more of said pits flanking a land are of sufficient depth to form alight-reflecting interferometer when the transient optical statematerial is in its first state but not in its second state, uponinterface with said reading beam.
 4. The optical disc of claim 3 whereinR₆, R₇, R₈, and R₉ are propyl or hexyl and R₁, R₂, R₃, R₄ and R₅ arehydrogen.
 5. The optical storage medium of claim 3 wherein saidtransient optical state change security material is opaque in its firstoptical state and translucent in its second optical state.
 6. Theoptical storage medium of claim 3 wherein said transient optical statechange security material is translucent in its first optical state andopaque in its second optical state.
 7. An optical disc readable by anoptical reader generating a reading beam comprising: a substrate havingfirst major surface with one or more information pits and lands thereon,and a second major surface that is relatively planar, said informationpits and lands convertible into digital data bits when read through thesecond major surface by said reading reading beam of said opticalreader; a transient optical state change security material capable ofexisting in a first unactivated state and a second activated state,comprising:

where R₆, R₇, R₈, and R₉ are alkylamino and R₁, R₂, R₃, R₄ and R₅ areselected from the group consisting of hydrogen, alkyl, aryl, alkoxy,thioalkoxy, alkylamino, nitro, amino and halogen; wherein said transientoptical state change security material being selectively applied alongthe first major surface so as to provide an erroneous digital data bitread when the transient state change security material is in its firstunactivated state and its second activated state.
 8. The optical disc ofclaim 7 wherein R₆, R₇, R₈, and R₉ are propyl or hexyl and R₁, R₂, R₃,R₄ and R₅ are hydrogen.
 9. An optical medium comprising a compound ofthe following structure:

where R₆, R₇, R₈, and R₉ are alkylamino and R₁, R₂, R₃, R₄ and R₅ areselected from the group consisting of hydrogen, alkyl, aryl, alkoxy,thioalkoxy, alkylamino, nitro, amino and halogen; and wherein saidcompound is applied to an optical medium and is detectable on saidoptical medium by an optical reader producing a wavelength of from about630 nm to about 660 nm by a transient change in optical state from aninitial optical state to a second optical state.
 10. The optical mediumof claim 9 wherein the compound is associated with an optical datadeformation in a manner such that the read of the optical datadeformation is different when the compound is in its initial opticalstate and its second optical state.
 11. A method for authenticating anoptical medium having a number of data deformations thereon, said methodcomprising the steps of: (1) providing for a complementary data stateonto a portion of said optical medium; (2) detecting said complementarydata state on said portion of said optical medium. (3) authenticatingsaid optical medium upon detection of said complementary data state onsaid pottion of said optical medium; wherein the complementary datastate is produced using a transient optical state security materialcomprising:

where R₆, R₇, R₈, and R₉ are alkylamino and R₁, R₂, R₃, R₄ and R₅ areselected from the group consisting of hydrogen, alkyl, aryl, alkoxy,thioalkoxy, alkylamino, nitro, amino and halogen.
 12. The method ofclaim 11 wherein said complementary data state entails a change from onevalid data state to a different valid data state.
 13. The method ofclaim 11 wherein said complementary data state entails a change from oneerroneous data state to a different erroneous data state.
 14. The methodof claim 11 wherein said complementary data state entails a change froma valid data state to an erroneous data state.
 15. The method of claim11 wherein said complementary data state entails a change from anerroneous data state to a valid data state.
 16. The method of claim 11wherein R₆, R₇, R₈, and R₉ are propyl or hexyl and R₁, R₂, R₃, R₄ and R₅are hydrogen with respect to the transient optical state securitymaterial.